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Before the big bang: something or nothing

Has the cosmos existed forever, or did something bring it into existence? Time to grapple with the universe's greatest mystery

By Marcus Chown

AS BIG questions go, it’s hard to beat. Has the universe existed forever? Over the years, some of the greatest minds in physics have argued that no matter how far back in time you go, the universe has always been here. Others have argued that the opposite must be true – something must have happened to bring the cosmos into existence. With both sides claiming that observations support their view, until recently an answer seemed as distant as ever.

However, earlier this year, cosmologists Alex Vilenkin and Audrey Mithani claimed to have settled the debate. They have uncovered reasons why the universe cannot have existed forever. Yet what nature grudgingly gives with one hand, it takes back with the other – even though the universe has a beginning, its origins may be lost in the mists of time.

Modern cosmology began in 1916 when Einstein applied his newly formulated theory of gravity, general relativity, to the biggest gravitating mass he could think of&colon; the entire universe. Like Newton, Einstein favoured an unchanging universe – a universe that had existed forever and therefore had no beginning. To achieve this, Einstein realised that the gravity pulling together all the matter in the universe had to be countered by a weird cosmic repulsion of empty space.

Einstein’s static universe was unfortunately unstable. As the English physicist Arthur Eddington pointed out, such a universe was balanced on a knife-edge between runaway expansion and runaway contraction. A further blow came in 1929 when American astronomer Edwin Hubble observed that galaxies were flying apart from each other like pieces of cosmic shrapnel. The conclusion was that the universe was expanding. …